CN116625566A - Continuous measuring method for real three-dimensional stress of engineering rock mass - Google Patents

Abstract

The application discloses a continuous measurement method for real three-dimensional stress of an engineering rock mass, which comprises the following steps: mounting a hollow inclusion sensor at a measuring point, recording the polar angle and the axial deflection angle of each channel, and obtaining a first strain value of each channel of the hollow inclusion sensor at a certain moment after the mounting is completed; drilling a thick-wall cylindrical rock core coaxial with the hollow inclusion by adopting a trepanning stress relief method, continuously measuring strain values of all channels, and obtaining a second strain value of the final stable state of each channel; and calculating the real three-dimensional stress state of the measuring point at a certain moment by adopting a thick-wall cylinder elasticity theory based on the difference value between the second strain value and the first strain value at a certain moment of each channel of the hollow inclusion sensor. According to the application, the three-dimensional real stress value of the measuring point corresponding to each moment is calculated by adopting the elastic solution of the periphery of the round hole of the composite structure, and the real stress state of the surrounding rock is reflected.

Description

A real three-dimensional stress continuous measurement method of engineering rock mass

technical field

The invention belongs to the field of rock mass stress testing, in particular to a method for continuously measuring real three-dimensional stress of engineering rock mass.

Background technique

The stress state of rock mass is an important parameter for evaluating the stability of engineering surrounding rock. During the construction of underground engineering, the stress in the rock mass will be redistributed, and the stress redistribution of rock mass will lead to local stress concentration, which in turn will lead to the destruction of the rock at the stress concentration location. . Therefore, a reasonable method must be used to obtain the true stress state of the key parts of the disturbed rock mass.

Since the rock mass stress cannot be directly measured, it can only be back-calculated based on the medium stress-strain relationship by measuring the changes in parameters such as rock mass or sensor displacement and strain caused by stress changes. Commonly used sensors include pressure cells, strain gauges (gauge), etc., but the pressure cell can only obtain the compressive stress perpendicular to the surface of the pressure cell, and the strain gauge (gauge) can only obtain the stress along the direction of the sensor, even if multiple different angles are used The sensor can only obtain the stress change in some directions relative to the initial state, not the real three-dimensional stress state of the measuring point, and the true three-dimensional stress of the medium is the only indicator to evaluate its stability. Therefore, stress relief must be performed on the basis of indirect physical quantity testing to obtain the true three-dimensional stress state of the measuring point. The continuous testing device and method for in-situ stress of coal and rock mass proposed by Wang Enyuan et al. (CN101514926B) put the capsule pressure sensor at the measuring point, and read the subsequent change of the pressure sensor with the help of the acquisition instrument, which is a single-component stress incremental testing technology . On this basis, a measuring device and method for continuously measuring the three-dimensional stress of coal and rock mass proposed by Chen Ying et al. (CN114235256A) replaces the capsule pressure sensor with a hollow inclusion stress gauge. Calculate the variation of the three-dimensional stress based on the variation of the sheet when the measuring point is disturbed. Zhou Gang et al. adopted the three-dimensional stress monitoring method in CN114235256A in the paper "Study on Stress Monitoring and Evolution Law of Stope of Fully Mechanized Mining Face in Chensilou Mine" (Journal of Coal Science, 2016), and studied the three-dimensional stress of the stope of fully mechanized mining face. Evolution law. However, the stress obtained by the above two methods and research results is the stress change increment, not the current real stress state of the measuring point.

In the stability evaluation of engineering rock mass, only the measurement of the real three-dimensional stress state of the rock mass has practical significance. The existing one-dimensional or three-dimensional stress increment test technology obviously cannot meet the actual needs.

Contents of the invention

The purpose of the present invention is to provide a method for continuous measurement of real three-dimensional stress of engineering rock mass, so as to solve the above-mentioned problems in the prior art.

In order to achieve the above object, the present invention provides a method for continuous measurement of real three-dimensional stress of engineering rock mass, comprising the following steps:

Installing hollow inclusion sensors at the measuring point, recording the polar angle and axial deflection angle of each channel, and obtaining the first strain value of each channel of the hollow inclusion sensor at a certain moment after the installation is completed;

Drilling a thick-walled cylindrical rock core coaxial with the hollow inclusion by using the casing stress relief method, continuously measuring the strain values of each channel, and obtaining the second strain value of the final stable state of each channel;

Based on the difference between the second strain value of each channel of the hollow inclusion sensor and the first strain value at a certain moment, the real three-dimensional stress state of the measuring point at a certain moment is calculated using the elastic theory of a thick-walled cylinder.

Optionally, the process of obtaining the first strain value of each channel of the hollow inclusion sensor at a certain moment after installation includes:

Drill a large hole at the measuring point, and the depth of the large hole is not less than 3 to 5 times the radius of the section of the cavern;

A small hole is drilled forward at the bottom of the large hole. The small hole is coaxial with the large hole. The diameter of the small hole is consistent with that of the hollow inclusion. The relationship with the orientation instrument, obtain the polar angle and axial deflection angle of each channel, and use adhesive to fix the outer wall of the hollow enclosure and the wall of the small hole;

A data acquisition instrument was used to continuously measure and record the strain value of each channel of the hollow inclusion, which was recorded as the first strain value.

Optionally, the process of obtaining the second strain value of the final steady state of each channel includes:

Continue along the wall of the large hole to take the thick-walled cylindrical core coaxial with the small hole, the depth of the casing is not less than the depth of the small hole, and with the increase of the release depth, the core gradually rebounds after losing the external stress constraint The deformation causes changes in the strain value of each channel of the hollow inclusion body. After the core is completely released, the final steady-state strain of each channel is obtained, which is recorded as the second strain value.

Optionally, the process of calculating the real three-dimensional stress state of the measuring point at a certain moment using the elastic theory of thick-walled cylinder includes:

calculating the difference between the second strain value and the first strain value;

Based on the difference, the hyperstatic equation of the normal strain equation of each channel is constructed according to the elastic solution around the circular hole of the composite structure under the three-dimensional stress, and the optimal solution of the hyperstatic equation is calculated by the least square method, which is the first strain The value corresponds to the real three-dimensional stress state of the measuring point at the moment.

Further, the process of calculating the difference between the second strain value and the first strain value includes:

Set the first strain value of each channel at the initial moment to The first strain value of each channel at time t is /> The second strain value is /> Then the difference between the second strain value and the first strain value at the initial moment or moment t is:

In the formula, and /> Respectively, the difference between the second strain value and the first strain value at the initial time or time t, i is the number of the hollow inclusion rosette, and j is the number of each rosette strain gauge.

Furthermore, the process of calculating the real three-dimensional stress state of the measuring point according to the elastic solution around the circular hole of the composite structure under three-dimensional stress includes:

Calculate the correction coefficient according to the geometric parameters and elastic parameters of the drilling and hollow inclusions;

calculating the stress coefficient based on the Poisson's ratio of the rock, the polar angle and axial deflection angle of each channel, and the correction coefficient of the strain gauge;

The real three-dimensional stress of the measuring point is calculated based on the stress coefficient.

Further, the calculation process of the correction coefficient includes:

Calculate the modulus ratio based on the shear modulus of the hollow inclusion sensor and the shear modulus of the rock;

Calculate the radius ratio based on the inner radius of the hollow inclusion sensor and the radius of the measured pinhole;

A correction factor for the strain gauge is calculated based on the modulus ratio and the radius ratio.

Furthermore, the construction process of the statically indeterminate equation of the normal strain equation of each channel includes:

Based on the difference between the second strain value of each channel and the first strain value, an equation equation between the normal strain of each channel and the current stress of the measuring point is constructed to form a statically indeterminate equation group;

Calculation of normal equations of hyperstatically indeterminate equations based on the principle of least squares;

Calculate the stress solution of the equation to obtain the real three-dimensional stress of the measuring point.

Technical effect of the present invention is:

The present invention proposes a method for continuous measurement of the real three-dimensional stress of engineering rock mass, which adopts the hollow inclusion stress release method to continuously measure the real stress of the measuring point, based on the first strain value of each channel at any time after the hollow inclusion is installed and the casing hole After the release, the difference between the second strain values in the stable state of each channel is used to calculate the three-dimensional real stress value of the measuring point corresponding to each moment by using the elastic solution around the circular hole of the composite structure to reflect the real stress state of the surrounding rock.

Description of drawings

The drawings constituting a part of the application are used to provide further understanding of the application, and the schematic embodiments and descriptions of the application are used to explain the application, and do not constitute an improper limitation to the application. In the attached picture:

Fig. 1 is the flow chart of the real three-dimensional stress continuous measurement method of engineering rock mass in the embodiment of the present invention;

Fig. 2 is a plan view of the working face advancing process in the embodiment of the present invention;

Fig. 3 is a sectional view of the advancing process of the working face in the embodiment of the present invention;

Fig. 4 shows the values of each channel of the working face advancing process sensor in the embodiment of the present invention.

Fig. 5 is the change curve of the strain of each strain gauge at the measuring hole during the advancing process;

Fig. 6 is the strain change curve of each strain gauge at the measuring hole during the lifting process;

Figure 7 is the stress component change curve during the propulsion process.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

It should be noted that the steps shown in the flowcharts of the accompanying drawings may be performed in a computer system, such as a set of computer-executable instructions, and that although a logical order is shown in the flowcharts, in some cases, The steps shown or described may be performed in an order different than here.

The terms "first", "second" and the like in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific sequence or sequence. It should be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application can be practiced in sequences other than those illustrated or described herein, and that references to "first," "second," etc. distinguish Objects are generally of one type, and the number of objects is not limited. For example, there may be one or more first objects. In addition, "and/or" in the specification and claims means at least one of the connected objects, and the character "/" generally means that the related objects are an "or" relationship.

Embodiment one

As shown in Figures 1-4, a method for continuously measuring the real three-dimensional stress of engineering rock mass is provided in this embodiment, as shown in Figure 1, comprising the following steps:

Drill a large hole at the measuring point, and the depth of the large hole is not less than 3 to 5 times the radius of the section of the cavern;

A small hole is drilled forward at the bottom of the large hole. The small hole is coaxial with the large hole. The diameter of the small hole is consistent with that of the hollow inclusion. The relationship with the orientation instrument, the polar angle and axial deflection angle of each channel are obtained, and the outer wall of the hollow enclosure is fixed with the wall of the small hole with an adhesive, as shown in Figure 2 and Figure 3;

Use the data acquisition instrument to continuously measure and record the strain value of each channel of the hollow inclusion, and record it as the first strain value;

Continue along the wall of the large hole to take the thick-walled cylindrical core coaxial with the small hole, the depth of the casing is not less than the depth of the small hole, and with the increase of the release depth, the core gradually rebounds after losing the external stress constraint Deformation causes changes in the strain values of each channel of the hollow inclusion body. After the core is completely released, the final stable state strain of each channel is obtained, which is recorded as the second strain value, as shown in Figure 4;

calculating the difference between the second strain value and the first strain value;

Based on the difference, the hyperstatic equations of the positive strain equations of each channel are constructed according to the elastic solution around the circular hole of the composite structure under the three-dimensional stress, and the optimal solution of the hyperstatic equations is calculated by the least square method, and the first strain value is calculated. The real three-dimensional stress state of the measuring point at the corresponding moment.

As a preferred implementation of the present application, in the process of calculating the difference between the second strain value and the first strain value, the first strain value of each channel at the initial moment is set to The first strain value of each channel at time t is The second strain value is /> Then the difference between the second strain value and the first strain value at the initial moment or moment t is:

In the formula, and /> Respectively, the difference between the second strain value and the first strain value at the initial time or time t, i is the number of the hollow inclusion rosette, and j is the number of each rosette strain gauge.

As a preferred embodiment of the present application, the process of calculating the real three-dimensional stress state of the measuring point at the moment corresponding to the first strain value includes:

The correction coefficient is calculated according to the geometric parameters and elastic parameters of the borehole and the hollow inclusion, and the steps are as follows:

Calculate the modulus ratio n based on the shear modulus G ₀ of the hollow inclusion sensor and the shear modulus G of the rock:

n=G ₀ /G

Calculate the radius ratio m based on the inner radius R ₀ of the hollow inclusion sensor and the measured hole radius R:

m=R ₀ /R

Calculate modulus radius coefficients d ₁ , d ₂ , d ₃ ,..., d ₆ according to radius ratio m and modulus ratio n:

In the formula, D=(1+xn)[x ₀ +n+(1-n)(3m ² -6m ⁴ +4m ⁶ )]+(x ₀ -x)m ² [(1-n)m ⁶ +x ₀ +n], x ₀ =3-4ν ₀ , x=3-4ν.

Calculate the correction factors K ₁ , K ₂ , K ₃ , K ₄ of the strain gauge according to the modulus radius coefficients d ₁ , d ₂ , d ₃ ,..., d ₆ :

After the calculation of the correction coefficient is completed, the stress coefficients A ₁ , A ₂ , A ₃ , ..., A ₆ are calculated based on the Poisson's ratio of the rock, the polar angle and axial deflection angle of each channel, and the correction coefficient of the strain gauge:

In the formula, θ _i is the polar angle corresponding to the rosette; is the angle of the strain gauge.

As a preferred embodiment of the present application, the process of calculating the three-dimensional stress at the measuring point according to the elastic solution around the circular hole of the composite structure under the three-dimensional stress includes:

Finally, the normal strain equations of each channel are constructed according to the stress coefficients A ₁ , A ₂ , A ₃ ,..., A ₆ :

Eδε＝A ₁ σ _x +A ₂ σ _y +A ₃ σ _z +A ₄ τ _xy +A ₅ τ _yz +A ₆ τ _zx

In the formula, δε is the difference between the second strain value and the first strain value of the strain gauge.

Based on the difference between the second strain value of each channel and the first strain value, the equation equation between the normal strain of each channel and the current stress of the measuring point is constructed, and the hyperstatic equations are constructed, and the normal equation is calculated:

In the formula, s is the number of observation value equations, and s=mn; m is the number of rosettes; n is the number of strain gauges in different directions for each rosette;

Calculate the stress solution of the method equation to obtain the real three-dimensional stress of the measuring point.

Embodiment two

Taking the real three-dimensional stress test of the roof during the advancing process of a fully-mechanized mining face in a coal mine as an example, a hollow inclusion is installed 100m in front of the measuring point on the excavation section and the data is recorded, and the excavation surface is released after it exceeds 140m from the section where the test point is located. The specific material parameters are : Elastic modulus of drilling surrounding rock E＝25GPa, Poisson’s ratio v＝0.159; inclusion material E ₀ ＝7.5GPa, Poisson’s ratio v ₀ ＝0.38, release radius R＝50mm during release process, hollow inclusion radius R ₀ = 45mm. As the excavation advances, the measured data are shown in Tables 1-3, and the change curves are shown in Figures 5-7: Table 1 shows the strain gauge strain at the measuring point during the advancing process, and Table 2 shows the strain gauge strain at the measuring point during the lifting process , Table 3 shows the stress components at the measuring points during the propulsion process.

Table 1 Strain value of each channel at the measuring point during the propulsion process (με)

Table 2 The strain of each channel at the measuring point during the lifting process (με)

Table 3 The real three-dimensional stress component of the measuring point during the propulsion process (MPa)

The present invention proposes a method for continuous measurement of the real three-dimensional stress of engineering rock mass, which adopts the hollow inclusion stress release method to continuously measure the real stress of the measuring point, based on the first strain value of each channel at any time after the hollow inclusion is installed and the casing hole After the release, the difference between the second strain values in the stable state of each channel is used to calculate the three-dimensional real stress value of the measuring point corresponding to each moment by using the elastic solution around the circular hole of the composite structure to reflect the real stress state of the surrounding rock.

The above is only a preferred embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in this application Replacement should be covered within the protection scope of this application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (8)

1. A real three-dimensional stress continuous measurement method of engineering rock mass, is characterized in that, comprises the following steps: Installing hollow inclusion sensors at the measuring point, recording the polar angle and axial deflection angle of each channel, and obtaining the first strain value of each channel of the hollow inclusion sensor at a certain moment after the installation is completed; Drilling a thick-walled cylindrical rock core coaxial with the hollow inclusion by using the casing stress relief method, continuously measuring the strain values of each channel, and obtaining the second strain value of the final stable state of each channel; Based on the difference between the second strain value of each channel of the hollow inclusion sensor and the first strain value at a certain moment, the real three-dimensional stress state of the measuring point at a certain moment is calculated using the elastic theory of a thick-walled cylinder. 2. the real three-dimensional stress continuous measurement method of engineering rock mass according to claim 1, is characterized in that, the process of obtaining the first strain value at a certain moment in each channel of the hollow inclusion sensor after installation comprises: Drill a large hole at the measuring point, and the depth of the large hole is not less than 3 to 5 times the radius of the section of the cavern; A small hole is drilled forward at the bottom of the large hole. The small hole is coaxial with the large hole. The diameter of the small hole is consistent with that of the hollow inclusion. The relationship with the orientation instrument, obtain the polar angle and axial deflection angle of each channel, and use adhesive to fix the outer wall of the hollow enclosure and the wall of the small hole; A data acquisition instrument was used to continuously measure and record the strain value of each channel of the hollow inclusion, which was recorded as the first strain value. 3. engineering rock mass real three-dimensional stress continuous measurement method according to claim 1, is characterized in that, the process of obtaining the second strain value of described each channel final steady state comprises: Continue along the wall of the large hole to take the thick-walled cylindrical core coaxial with the small hole, the depth of the casing is not less than the depth of the small hole, and with the increase of the release depth, the core gradually rebounds after losing the external stress constraint The deformation causes changes in the strain value of each channel of the hollow inclusion body. After the core is completely released, the final steady-state strain of each channel is obtained, which is recorded as the second strain value. 4. the real three-dimensional stress continuous measurement method of engineering rock mass according to claim 1, is characterized in that, adopts thick-walled cylinder elastic theory to calculate the process of the real three-dimensional stress state of measuring point at a certain moment and comprises: calculating the difference between the second strain value and the first strain value; Based on the difference, the hyperstatic equations of the positive strain equations of each channel are constructed according to the elastic solution around the circular hole of the composite structure under the three-dimensional stress, and the optimal solution of the hyperstatic equations is calculated by the least square method, and the first strain value is calculated. The real three-dimensional stress state of the measuring point at the corresponding moment. 5. The real three-dimensional stress continuous measurement method of engineering rock mass according to claim 4, wherein the process of calculating the difference between the second strain value and the first strain value comprises: Set the first strain value of each channel at the initial moment The first strain value of each channel at time t is The second strain value is /> Then the difference between the second strain value and the first strain value at the initial moment or moment t is: In the formula, and /> Respectively, the difference between the second strain value and the first strain value at the initial time or time t, i is the number of the hollow inclusion rosette, and j is the number of each rosette strain gauge. 6. The real three-dimensional stress continuous measurement method of engineering rock mass according to claim 4, is characterized in that, the process of calculating the real three-dimensional stress state of the measuring point at the corresponding moment of the first strain value comprises: Calculate the correction coefficient according to the geometric parameters and elastic parameters of the drilling and hollow inclusions; calculating the stress coefficient based on the Poisson's ratio of the rock, the polar angle and axial deflection angle of each channel, and the correction coefficient of the strain gauge; The real three-dimensional stress of the measuring point is calculated based on the stress coefficient. 7. The real three-dimensional stress continuous measurement method of engineering rock mass according to claim 6, is characterized in that, the calculation process of described correction coefficient comprises: Calculate the modulus ratio based on the shear modulus of the hollow inclusion sensor and the shear modulus of the rock; Calculating the radius ratio based on the inner radius of the hollow inclusion sensor and the radius of the measured pinhole; A correction factor for the strain gauge is calculated based on the modulus ratio and the radius ratio. 8. the real three-dimensional stress continuous measurement method of engineering rock mass according to claim 4, is characterized in that, according to three-dimensional stress, the process of constructing each channel positive strain equation hyperstatic equation according to the elastic solution around the composite structure circular hole comprises: Based on the difference between the second strain value of each channel and the first strain value, an equation equation between the normal strain of each channel and the current stress of the measuring point is constructed to form a statically indeterminate equation group; Calculation of normal equations of hyperstatic equations based on least squares principle; Calculate the stress solution of the method equation to obtain the real three-dimensional stress of the measuring point.